A thin film electroluminescent device generally has a cross sectional view as shown in FIG. 4. A transparent electrode 2 is formed on a glass substrate in the form of stripes, and a lower insulation layer 3, which is composed of an SiO.sub.2 layer 3a and an Si.sub.3 N.sub.4 layer 3b, is formed thereon. A luminescent layer 4 is then formed on the insulation layer 3 by an electron beam vapor deposition method, and a transparent upper insulation layer 5, which is composed of an Si.sub.3 N.sub.4 layer 5a and an Al.sub.2 O.sub.3 layer 5b, is formed thereon by a sputtering method. An aluminum back electrode 6 is formed on the upper insulation layer 5 by a chemical etching method in the form of stripes which are perpendicular to the lower transparent electrode 2. A voltage is applied between the transparent electrode 2 and the back electrode 6 to emit light in the luminescent layer 4 and the light comes out through the glass substrate 1.
However, since the luminescent layer 4 is formed by the electron beam vapor deposition, the initially formed portion has poor crystallinity, called "dead layer". Accordingly, in order to obtain high luminance, the luminescent layer 4 should be made thick, which adversely increase the driving voltage. The present inventors propose in Japanese Patent Application Ser. No. 117943/1988 that the problem is dissolved by producing the luminescent layer 4 by a chemical vapor deposition (CVD) method.
The CVD method, however, forms the luminescent layer as surrounding the substrate, thus the layer covering all the surface of the substrate, as indicated the layer 4 of FIG. 1. The unnecessary portion of the luminescent layer 4 should be removed, so that an etching step is inevitable and causes the cost-up of the obtained products.